(1) Field of the Invention
The present invention relates to a process for producing a glass and particularly to a process for producing a glass, wherein a large-sized glass can be produced efficiently according to a sol-gel process without requiring a complex procedure.
(2) Description of the Prior Art
The processes for glass production include the so-called sol-gel process using a metal alkoxide. This sol-gel process for glass production has been considered to be unsuitable for production of a large-sized glass, because in the process the dried gel obtained by the drying treatment after gelation tends to have cracks.
Meanwhile, Japanese Patent Application Kokai (Laid-Open) No. 131833/1985 discloses a sol-gel process for producing a large-sized glass which had been impossible to obtain according to the prior sol-gel process. As is clear from the description made in Examples of said patent document, the process comprises mixing a metal alkoxide (e.g. silicon ethoxide) with an acid (e.g. hydrochloric acid); vigorously stirring the mixture; adding an ultrafine silica powder thereto with stirring; applying an ultrasonic vibration thereto; removing the resulting clusters by centrifugation; adjusting the pH of the obtained solution with a basic catalyst; and then effecting gelation, drying and heating in this order. The process, however, has problems in that not only the steps are complex but also the clusters are present even after the ultrasonic vibration and need be removed by centrifugation.
Thus, the process disclosed in Japanese Patent Application Kokai (Laid-Open) No. 131833/1985 can produce a relatively large-sized glass according to a sol-gel process, but uses very complex steps and requires, for example, ultrafine silica powder addition, ultrasonic vibration and centrifugation.